The parents in Overland Park, Kan., were fed up. They wanted their children off screens, but they needed strength in numbers. First, because no one wants their kid to be the lone weird one without a phone. And second, because taking the phone away from a middle schooler is actually very, very tough.

“We start the meetings by saying, ‘This is hard, we’re in a new frontier, but who is going to help us?’” said Krista Boan, who is leading a Kansas City-based program called START, which stands for Stand Together And Rethink Technology. “We can’t call our moms about this one.”

For the last six months, at night in school libraries across Overland Park, a suburb of Kansas City, Mo., about 150 parents have been meeting to talk about one thing: how to get their children off screens.

It wasn’t long ago that the worry was that rich students would have access to the internet earlier, gaining tech skills and creating a digital divide. Schools ask students to do homework online, while only about two-thirds of people in the U.S. have broadband internet service. But now, as Silicon Valley’s parents increasingly panic over the impact screens have on their children and move toward screen-free lifestyles, worries over a new digital divide are rising. It could happen that the children of poorer and middle-class parents will be raised by screens, while the children of Silicon Valley’s elite will be going back to wooden toys and the luxury of human interaction.

This is already playing out. Throwback play-based preschools are trending in affluent neighborhoods — but Utah has been rolling out a state-funded online-only preschool, now serving around 10,000 children. Organizers announced that the screen-based preschool effort would expand in 2019 with a federal grant to Wyoming, North Dakota, South Dakota, Idaho and Montana.

Lower-income teenagers spend an average of eight hours and seven minutes a day using screens for entertainment, while higher income peers spend five hours and 42 minutes, according to research by Common Sense Media, a nonprofit media watchdog. (This study counted each screen separately, so a child texting on a phone and watching TV for one hour counted as two hours of screens being used.) Two studies that look at race have found that white children are exposed to screens significantly less than African-American and Hispanic children.

The psychologist Richard Freed, who wrote a book about the dangers of screen-time for children and how to connect them back to real world experiences, divides his time between speaking before packed rooms in Silicon Valley and his clinical practice with low-income families in the far East Bay, where he is often the first one to tell parents that limiting screen-time might help with attention and behavior issues.

“I go from speaking to a group in Palo Alto who have read my book to Antioch, where I am the first person to mention any of these risks,” Dr. Freed said.

He worries especially about how the psychologists who work for these companies make the tools phenomenally addictive, as many are well-versed in the field of persuasive design (or how to influence human behavior through the screen). Examples: YouTube next video autoplays; the slot machine-like pleasure of refreshing Instagram for likes; Snapchat streaks.

“The digital divide was about access to technology, and now that everyone has access, the new digital divide is limiting access to technology,” said Chris Anderson, the former editor of Wired magazine.

Technology Is a Huge Social Experiment on Children

Some parents, pediatricians and teachers around the country are pushing back.

“These companies lied to the schools, and they’re lying to the parents,” said Natasha Burgert, a pediatrician in Kansas City. “We’re all getting duped.”

“Our kids, my kids included, we are subjecting them to one of the biggest social experiments we have seen in a long time,” she said. “What happens to my daughter if she can’t communicate over dinner — how is she going to find a spouse? How is she going to interview for a job?”

She and her husband, who runs a decorative concrete company, keep their children away from cellphones but found that even a little exposure to screen time changed the boys’ behavior. Her older son, who has A.D.H.D., would get angry when the screen had to be turned off, she said, which worried her.

His Christmas wish list was a Wii, a PlayStation, a Nintendo, a MacBook Pro and an iPhone.

“And I told him, ‘Kiddo, you’re not gonna get one of those things,’” Ms. Brownsberger said. “Yeah, I’m the mean mom.”

But one thing has made it easier: Others in what she described as a rural neighborhood outside Kansas City are doing the same thing.

“It takes a community to support this,” she said. “Like I was just talking to my neighbor last night — ‘Am I the worst mom ever?’”

Ms. Boan has three pilots running with about 40 parents in each, looking at best practices for getting kids off phones and screens. Overland Park’s Chamber of Commerce is supporting the work, and the city is working to incorporate elements of digital wellness into its new strategic vision.

“The city planner and the chamber of commerce said to us, ‘We’ve seen this impact our city,’” Ms. Boan said. “We all want our kids to be independent, self-regulated device users, but we have to equip them.”

The Privilege of Choices

In Silicon Valley, some feel anxious about the growing class divide they see around screen-time.

Kirstin Stecher and her husband, who works as an engineer at Facebook, are raising their kids almost completely screen-free.

“Is this coming from a place of information — like, we know a lot about these screens,” she said. “Or is it coming from a place of privilege, that we don’t need them as badly?”

“There’s a message out there that your child is going to be crippled and in a different dimension if they’re not on the screen,” said Pierre Laurent, a former Microsoft and Intel executive now on the board of trustees at Silicon Valley’s Waldorf School. “That message doesn’t play as well in this part of the world.”

“People in this region of the world understand that the real thing is everything that’s happening around big data, AI, and that is not something that you’re going to be particularly good at because you have a cellphone in fourth grade,” Mr. Laurent said.

Google published a case study of its work with the Hoover City, Ala., school district, saying technology equips students “with skills of the future.”

The company concluded that its own Chromebooks and Google tools changed lives: “The district leaders believe in preparing students for success by teaching them the skills, knowledge, and behaviors they need to become responsible citizens in the global community.”

Dr. Freed, though, argues these tools are too relied upon in schools for low-income children. And he sees the divide every day as he meets tech-addicted children of middle and low-income families.

“For a lot of kids in Antioch, those schools don’t have the resources for extracurricular activities, and their parents can’t afford nannies,” Dr. Freed said. He said the knowledge gap around tech’s danger is enormous.

Dr. Freed and 200 other psychologists petitioned the American Psychological Association in August to formally condemn the work psychologists are doing with persuasive design for tech platforms that are designed for children.

A version of this article appears in print on , Section B, Page 3 of the New York edition with the headline: Rich Parents Ban Devices As the Poor Grow Reliant. Order Reprints | Today’s Paper | Subscribe